Lighting assembly

ABSTRACT

A lighting assembly includes a light source, a light guiding plate and a reflecting member. The light guiding plate has a light input surface, a light output surface extending from the light input surface, a connecting surface and a reflecting surface. The connecting surface has an inclined segment. Extensions of the inclined segment and the light output surface cooperatively define a first included angle. The reflecting surface interconnects the connecting surface and the light output surface, cooperates with the light output surface to define a second included angle, and mounted with the reflecting member. A thickness of the light guiding plate at the reflecting surface is greater than that at the light input surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation patent application of U.S. patentapplication Ser. No. 14/148,058 filed on Jan. 6, 2014 which claimspriority of Taiwanese Application No. 102118628, filed on May 27, 2013.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an optical device, more particularly to a lightguiding assembly incorporating a light guiding device and a lightsource.

2. Description of the Related Art

A long fluorescent lamp or multiple round light bulbs are often used inexhibition venues where sufficient lighting for a long or large displayarea is required. However, the light emitted by a single fluorescentlamp tends to be scattered and inefficient, and the light from multipleround light bulbs tends to overlap and is thus uneven. In addition,increasing the number of lamps also increases the costs of lighting.

A light guiding device is often used to regulate light emitted from alight source for a more even lighting effect. U.S. Pat. No. 6,328,453and U.S. Pat. No. 6,752,507 disclose light guiding plates with microstructures formed thereon for controlling directions of light outputtedfrom the light guiding plates to result in a relatively even lightingeffect. However, designing and processing the micro structures on thelight guiding plates increases the manufacturing complexity and costs.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide a lightingassembly including a light guiding device that is able to manipulate anilluminating region without micro structures to alleviate the aforesaiddrawbacks of the prior art.

According to the present invention, a lighting assembly includes a lightsource capable of emitting light, a light guiding plate and a reflectingmember. The light guiding plate has a light input surface, a lightoutput surface, a connecting surface and a reflecting surface. The lightoutput surface extends from the light input surface. The connectingsurface is opposite to the light output surface and has an inclinedsegment inclining away from the light output surface. Extensions of theinclined segment and the light output surface cooperatively define afirst included angle therebetween. The reflecting surface interconnectsthe connecting surface and the light output surface, and cooperates withthe light output surface to define a second included angle therebetween.A thickness of the light guiding plate at the reflecting surface isgreater than that at the light input surface. The reflecting member ismounted to the reflecting surface of the light guiding plate.

The lighting assembly according to the present invention is able toregulate scattered light emitted from the light source into an evenlight projection that is suitable for illuminating a large area. Theparameters of the light guiding plate can be changed during themanufacturing process to control the luminous flux of the light exitingthe light guiding plate.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present disclosure will becomeapparent in the following detailed description of the preferredembodiment with reference to the accompanying drawings, of which:

FIG. 1 is an exploded perspective view of a preferred embodiment of alighting assembly according to the present invention;

FIG. 2 is a side view of a light guiding device of the preferredembodiment; and

FIG. 3 is a side view of a variation of the light guiding device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIG. 1, the preferred embodiment of a lightingassembly 2 according to the present invention includes a light guidingdevice 20 and a light source 21. The light guiding device 20 includes alight guiding plate 22 for receiving light emitted from the light source21, and a reflecting member 23 mounted to the light guiding plate 22. Inthis embodiment, the light source 21 includes a plurality of lightemitting diodes (LEDs) 211, but it is not limited thereto.

With further reference to FIG. 2, the light guiding plate 22 has a lightinput surface 221, a light output surface 222, a connecting surface 223and a reflecting surface 224. The light input surface 221 has a firstedge 225 and a second edge 226 opposite to each other in a firstdirection (D1). The light output surface 222 extends from the first edge225 of the light input surface 221 in a second direction (D2) transverseto the first direction (D1), and has a distal edge 230 opposite to thefirst edge 225 of the light input surface 221. The connecting surface223 is opposite to the light output surface 222 in the first direction(D1), and has a straight segment 229 extending from the second edge 226of the light input surface 221 and an inclined segment 220 extendingfrom the straight segment 229, inclining away from the light outputsurface 222 and terminating at an end edge 227. In this embodiment, thestraight segment 229 of the connecting surface 223 is parallel to thelight output surface 222. The reflecting surface 224 interconnects theend edge 227 of the connecting surface 223 and the distal edge 230 ofthe light output surface 222. Extensions of the inclined segment 220 ofthe connecting surface 223 and the light output surface 222cooperatively define a first included angle θ therebetween. Thereflecting surface 224 and the light output surface 222 cooperativelydefine a second included angle φ therebetween. A distance between thesecond edge 226 of the light input surface 221 and the end edge 227 ofthe connecting surface 223 in the second direction (D2) is shorter thanthat between the first edge 225 of the light input surface 221 and thedistal edge 230 of the light output surface 222.

With the above mentioned configuration, relationships of θ<φ, θ<θ_(T)and L≧(AD)/tan θ are satisfied, where θ_(T) is a critical angle fortotal internal reflection associated with the light guiding plate 22,(AD) is a distance between a location of incidence of a light beam onthe light input surface 221 and one of the first edge 225 and the secondedge 226 of the light input surface 221, and (L) is the distance betweenthe second edge 226 of the light input surface 221 and the end edge 227of the connecting surface 223 in the second direction (D2). The secondincluded angle φ is a parameter for controlling an angle of beam exitingthe light guiding plate 22, and the distance (L) and the first includedangle θ are parameters for controlling a width of beam exiting the lightguiding plate 22. These three parameters cooperatively control theluminous flux of the light exiting the light guiding plate 22.

The reflecting member 23 is mounted to the reflecting surface 224 of thelight guiding plate 22. The light emitted by the light source 21 entersthe light guiding plate 22 via the light input surface 221, and part ofthe light is reflected by the reflecting member 23 to exit the lightguiding plate 22 through the light output surface 222.

Light guiding plates 22 of two different materials, Polycarbonate (PC)and Polymethylmethacrylate (PMMA), and with different dimensions aremade for testing purposes. In the tests, the light measured at the lightinput surface 221 is 90.67 lm, and the LEDs 211 of the light source 21were linearly arranged and correspond in position to the central axis ofthe light input surface 221 (see FIG. 1), such that AD=(d/2) where (d)is the distance between the first edge 225 and the second edge 226 ofthe light input surface 221. The light output of each test group ismeasured in lm and percentages of the light output with respect to thelight input are computed, and the test results are shown in Tables 1 and2.

It is noted herein that AD may vary depending on the position andorientation of the LEDs 211 that affect the angle and position ofincidence of the light beam on the light input surface 221. A condensedlighting effect may still be achieved if AD is varied such as when AD is0.3 d or 0.7 d.

Referring to Table 1, test group (1) satisfies all the above mentionedthree relationships where θ<φ (11°<30°), θ<θ_(T) (11°<42.16°) andL≧(d/2)/tan θ (79 mm>2.2 mm). Therefore, 90% efficiency is achieved.Test group (2) has a similar result to group (1).

Test groups (3) to (6) show that the efficiency is reduced proximatelyto 50% or less if any of the three relationships is not satisfied.

TABLE 1 Material PMMA Index of 1.49 Reflection (n) Critical 42.16° Angle(θ _(T)) d (mm) 4 (d/2)/(tanθ_(T)) (mm) 2.2 Flux of 90.67 light at thelight input surface (lm) L (mm) 79 79 79 79 2 79 φ 30 44 44 44 44 44 θ(°) 11 11 42.16 44 11 50 Flux of 81.8 86.5 47.4 48.1 42.2 48.8 light atthe light output surface (lm) Ratio of 90.2 95.4 52.3 53 46.5 53.8 LightOutput to Light Input (%) Test Group Number (1) (2) (3) (4) (5) (6)

Table 2 indicates similar results from experiments carried out with thelight guiding devices 20 whose light guiding plates 22 are made of PC.

TABLE 2 Material PC Index of 1.59 Reflection (n) Critical 38.97° Angle(θ _(T)) d (mm) 4 (d/2)/(tanθ_(T)) (mm) 2.5 L (mm) 79 79 79 79 2 79 φ 3044 44 44 44 44 θ (°) 11 11 42.16 44 11 50 Flux of 81.8 84.1 46.2 46.741.7 47.5 Light Input from the Light Guiding Plate (lm) Ratio of 90.295.4 50.9 51.5 46 52.4 Light Output to Light Input (%) Test Group Number(1) (2) (3) (4) (5) (6)

With reference to FIG. 3, an alternative design of the connectingsurface 223 without any segment parallel to the light output surface 222will obtain similar test results to those shown in Tables 1 and 2.

To conclude, the lighting assembly 2 according to the present inventionis able to regulate scattered light emitted from the light source 21into an even light projection that is suitable for illuminating a largearea. The parameters of the light guiding plate 22 can be changed duringthe manufacturing process to control the luminous flux of the lightexiting the light guiding plate 22.

While the present invention has been described in connection with whatis considered the most practical and preferred embodiment, it isunderstood that this invention is not limited to the disclosedembodiment but is intended to cover various arrangements included withinthe spirit and scope of the broadest interpretation so as to encompassall such modifications and equivalent arrangements.

What is claimed is:
 1. A lighting assembly comprising: a light sourcecapable of emitting light; a light guiding plate having a light inputsurface, a light output surface that extends from said light inputsurface, a connecting surface that is opposite to said light outputsurface, and that has an inclined segment inclining away from said lightoutput surface, extensions of said inclined segment and said lightoutput surface cooperatively defining a first included angletherebetween, and a reflecting surface that interconnects saidconnecting surface and said light output surface, and that cooperateswith said light output surface to define a second included angletherebetween, a thickness of said light guiding plate at said reflectingsurface being greater than that at said light input surface; and areflecting member for reflecting light emitted from said light guidingplate back into said light guiding plate.
 2. The lighting assembly ofclaim 1, wherein said connecting surface further has a straight segmentthat is connected between said inclined segment and said second edge ofsaid light input surface, and that is parallel to said light outputsurface.
 3. The lighting assembly of claim 1, wherein said light sourceincludes a plurality of light emitting diodes (LEDs) disposed linearlyalong an axis.
 4. The lighting assembly of claim 3, wherein the lengthof said light input surface is extended along said axis.
 5. The lightingassembly of claim 1, wherein said light input surface is a flat surfacewithout serration.
 6. The lighting assembly of claim 1, wherein thelength a projection of said light output surface on said connectingsurface is greater than the length of said connecting surface.
 7. Thelighting assembly of claim 1, wherein said reflecting surface of saidlight guide plate is covered by said reflecting member, and no surfaceof said light guiding plate other than said reflecting surface iscovered.
 8. The lighting assembly of claim 1, wherein said reflectingsurface is slanted with a constant slope rate.
 9. The lighting assemblyof claim 1, wherein said light output surface is directly exposed tosurroundings without being covered.
 10. The lighting assembly of claim1, wherein said light connecting surface is mirror surface withoutsandblasting.